1. Field of the Invention
This invention relates to a next process-determining method for determining a next process to be carried out next time based on sample data obtained by digitizing a sample object, an inspecting method for determining a next process based on image data obtained by picking up an image of an object to be inspected and carrying out the next process, and an inspecting apparatus for executing a predetermined process according to the inspecting method.
2. Description of the Related Art
For instance, to inspect whether or not a micro defect exists on the surface of a magnetic material layer (magnetic metal thin film) of a magnetic tape for recording various data, first, the surface of the magnetic material layer is magnified by hundreds of times by using an optical microscope and photographed in this state. Next, an operator visually checks based on the image of the photograph whether or not the surface has a flaw, a crack, a projection, or a depression, whether or not a deposition is formed thereon, and whether or not a foreign matter is attached thereto. After that, the quality of the magnetic tape is determined depending on the subjective judgment of the operator.
In an image defect detecting method (inspecting method) disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 11-242746, two types of data conversion processes opposite to each other are carried out on digital images taken of an object to be inspected, and a difference value between two image data items formed by the data conversion processes is calculated to thereby determine whether or not a defective portion exists. More specifically, first, a digital image of the object to be inspected is duplicated to produce two image data items. One of the image data items is subjected to dilate filter processing and then to erode filter processing, while the other of the image data items is subjected to the erode filter processing and then to the dilate filter processing. In this case, in the dilate filter processing, pixel data of colors near white (light colors) in the image data items are increased, whereas in the erode filter processing, pixel data of colors near black (dark colors) in the image data items are increased. As a result, in the one of the image data items, a defective portion whose image was picked up with pixels near white in color is emphasized, whereas in the other image data item, the defective portion whose image was picked up with pixels near black in color is emphasized. Next, a difference value between the one and the other of the image data items is calculated. Then, by comparing the difference value and a reference value (threshold) with each other, it is determined whether or not the digital image before the data conversion processes contained an image taken of the defective portion.
Further, in the wiring pattern checking method disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2000-251069, image data obtained by picking up an image of a wiring pattern on a printed circuit board is binarized by a predetermined processing method, and then the dilate filter processing and the erode filter processing are carried out on the binarized image data, whereby a disconnection of a trace in a wiring pattern or a short circuit between traces in the wiring pattern is detected. In this case, an image of an ultra-fine short-circuited portion, which was shown as a broken line in the unprocessed image data, is converted to an image of a linear unbroken line thicker than it actually is, in the binarized image data which has been subjected to the dilate filter processing. Further, an image of a half-disconnected portion, which was shown in the unprocessed image data as if it were connected, is converted to an image of a clearly disconnected portion, in the binarized image data which has been subjected to the erode filter processing. This enables a continuity-determining process to be executed so as to judge whether or not pixels X11, X12 corresponding to base points X1, X2, respectively, are connected by pixels identical in value of pixel data. Here, the base points X1, X1 are points at respective ends of an arbitrary trace in the wiring pattern, which should be connected to each other. If the pixels X11, X12 are not connected to each other, it can be determined that a disconnection exists in the trace between the base points X1, X1 in the wiring pattern. Further, the continuity-determining process may be executed as to connection between pixels Y11, Y12 corresponding to base points Y1, Y2 in respective traces, which should be insulated from each other. If the pixels Y11, Y12 are connected to each other, it can be determined that a short circuit exists between the traces in the wiring pattern to which the base points Y1, Y2 belong, respectively.
However, the above inspecting methods suffer from the following problems: The inspecting method of checking whether or not a micro defect exists in a photograph of the surface of an object to be inspected necessitates the operator's counting of defective portions formed on the surface by visual checking thereof, which results in a very low inspecting efficiency. Further, this inspecting method determines whether or not the object is a conforming item based on the count of defective portions, which depends on the subjectivity of the operator. Therefore, the criterion of the determination is different between operators, which makes it difficult to keep constant the quality level of inspected objects determined to be conforming items.
In the inspecting method disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 11-242746, two image data items are formed by picking up and duplicating an image of an object to be inspected, and subjected to the two types of data conversion processes opposite to each other, such that defective portions in both of the image data items can be emphasized, and then a difference value between the image data items is calculated and compared with a reference value (threshold), whereby the presence or absence of a defect is determined. Therefore, differently from the determining method dependent on the subjectivity of the operator, it is possible to determine the presence of a defect objectively. However, to carry out accurate determination by comparing the difference value and the reference value (threshold) with each other, it is necessary to increase the difference between image data containing an image of a defective portion and image data containing no image of a defective portion. Therefore, it is necessary to further emphasize the defective portion without degrading the image represented by the image data, when the filter processing is carried out on the image data, To meet the requirement, it is required to reduce the amount of conversion in each operation of the dilate filter processing and the erode filter processing, and repeat these operations a plurality of times. As a result, in this conventional inspecting method, it takes a very long processing time to determine whether the inspected object is a conforming item.
Further, in the inspecting method proposed by Japanese Laid-Open Patent Publication (Kokai) No. 2000-251069, the continuity-determining process is executed to determine whether or not processed image data has a sequence of continuous pixels identical in value of image data, for detecting a short circuit and a disconnection. However, although this inspecting method can determine continuity of pixels, it is difficult for this method to detect whether or not micro defects exist on the surface of the magnetic material layer of a magnetic tape. On the other hand, if the binarized image data having been subjected to the dilate filter processing and the binarized image data having been subjected to the erode filter processing are displaced on a display section, respectively, the operator can visually determine the presence or absence of a defect on the surface of the magnetic material layer. In such an inspecting method, however, similarly to the conventional inspecting method for checking whether or not a photograph taken of an object to be inspected contains an image of a micro defect, whether or not the object is a conforming item is determined in a manner dependent on the subjectivity of the operator. Therefore, the criterion of the determination is different between operators, which makes it difficult to keep constant the quality level of inspected objects determined to be conforming items.